Method of Surface Borehole Mining Using Horizontal Drilling Techniques

ABSTRACT

A method of horizontal directional drilling is provided. The proposed method utilizes directional drilling in which boreholes are arranged in a pattern such that the surface area of extraction is maximized. The pattern can be achieved using a vertical borehole, multiple lateral boreholes and multiple subsidiary portions of the lateral boreholes. A lateral borehole is drilled extending beyond a vertical borehole towards the orebody, from which a subsidiary borehole is drilled into the orebody. Once the extraction is complete, the subsidiary borehole is back filled. A new subsidiary borehole is drilled extending beyond the lateral borehole and adjacent to the first subsidiary borehole. The subsidiary boreholes are planned to form a honeycomb or direct stacked pattern. Once all extraction is complete from a lateral borehole and its subsidiary boreholes, a new lateral borehole is drilled from the vertical borehole and the process is repeated.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Patent Application No. 62/781,466 filed on Dec. 18, 2018, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The following relates to an improved process for surface borehole mining. More specifically, the following relates to a method of maximizing ore recovery per borehole, using multiple lateral boreholes drilled from a single vertical borehole.

BACKGROUND

Horizontal drilling of boreholes is well-known. A borehole is installed vertically from surface and into the waste rock near the orebody, and then a horizontal portion is drilled towards and into the orebody from which the ore can be drilled and extracted. The process begins by strategically positioning a hole on surface in the vicinity of an orebody via a collar location. A borehole is drilled down vertically from the collar location (the vertical borehole). Vertical boreholes can be permanently installed on surface and in the waste rock. Once the vertical borehole is installed, a horizontal portion can be drilled towards the orebody and into the ore (the lateral borehole).

One of the limitations of the existing methods is potentially low recovery of ore from each borehole. Therefore, there exists a need for minimizing costs and maximizing the efficiency of volume of material extracted from the ore.

SUMMARY

The following generally relates to an improvement to the methods for mining rocks and minerals, including surface borehole mining (SBM) methods applied through horizontal boreholes, to achieve operational efficiencies and cost savings, by reducing the amount of from-surface drilling and increasing the volume of material to be mined per borehole.

In one aspect there is provided a method to utilize directional drilling technology to drill a borehole from surface, steer the borehole horizontally, then employ multiple closely-spaced subsidiary holes from the borehole, to mine out the deposit in a substantially horizontal manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described with reference to the appended drawings wherein:

FIG. 1 illustrates a horizontally-drilled wellbore from the surface using surface boring techniques known in the art;

FIG. 2 illustrates a cross-sectional view of a lateral borehole near the vicinity of the ore with multiple subsidiary holes;

FIG. 3 illustrates a view of an embodiment of the lateral boreholes extending one by one beyond the parent borehole and into their desired positions using supplementary waste boreholes;

FIG. 4 illustrates a cross-sectional view of the boreholes within the high-grade ore, arranged in a closely-coupled nested honeycomb pattern;

FIG. 5 illustrates a cross-sectional view of the boreholes within the high-grade ore, arranged in a directly stacked honeycomb pattern;

FIG. 6 illustrates a cross-sectional comparison of the nested honeycomb pattern and a directly stacked honeycomb pattern;

FIG. 7 illustrates an isometric view of the end portion of the nested boreholes;

FIG. 8 illustrates a cross-sectional view of the ore body showing a first drilled subsidiary borehole;

FIG. 9 illustrates a cross-sectional view of the ore body showing a second drilled subsidiary borehole, with one back-filled previously drilled subsidiary borehole;

FIG. 10 illustrates a cross-sectional view of the ore body showing a third drilled subsidiary borehole, with two back-filled previously drilled subsidiary boreholes;

FIG. 11 illustrates a cross-sectional view of the ore body showing a fourth drilled subsidiary borehole, with three back-filled previously drilled subsidiary boreholes;

FIG. 12 illustrates a cross-sectional view of the ore body showing the subsidiary boreholes being drilled from left to right with a number of back-filled previously drilled subsidiary boreholes, and one subsidiary borehole being currently drilled;

FIG. 13 illustrates a cross-sectional view of the ore body showing the subsidiary boreholes being drilled from left to right at a next stage from FIG. 12; and

FIG. 14 illustrates a cross-sectional view of the ore body showing the subsidiary boreholes being drilled from left to right at a next stage from FIG. 13.

DETAILED DESCRIPTION

The surface borehole mining method disclosed herein considers the application of directional drilling technologies to selectively mine a deposit. Methods of designing a horizontal directional drilling system are also described herein. The directional drilling system comprises lateral boreholes arranged in a specific pattern to increase the scope and rate of extraction of ore from each borehole.

Boreholes are typically drilled from surface, collared vertically, steered through waste rock to a horizontal approach in proximity to the deposit, and continued horizontally through the ore.

FIG. 1 illustrates a typical drilled borehole. The process begins by strategically positioning a hole on the surface 105 in the vicinity of an orebody 103 via a collar location 106. A borehole is drilled vertically 101 from the collar location 106, then angled 102.

Once a vertical portion of the borehole 101 and the angled portion 102 are installed, a temporary horizontal portion 104 can be drilled towards and directly into the orebody 103. The vertical and angled portions of the borehole 101, 102 can be referred to together as the vertical borehole 100. The installation of the vertical borehole 100 can be permanent. The temporary horizontal portions of the borehole can be referred to as the lateral borehole 104.

An alternative method of surface borehole mining to increase the volume of material extracted from the ore is proposed herein, with the use of horizontal directional drilling at varying degrees of depth from a lateral borehole, permitting multiple lateral boreholes drilled from a single vertical borehole.

The directional drilling system comprises a permanent vertical borehole 101 drilled from a collar location 106 on surface 105 and angled laterally 102 (together, the vertical borehole). From the vertical borehole, a temporary lateral borehole 104 is extended and steered to be in a position parallel with the ore. In turn, from the lateral borehole, multiple closely spaced temporary subsidiary boreholes 201 can be drilled into the orebody to increase ore recovery rates.

This process can be repeated, such that there are multiple lateral boreholes 104 extending from the vertical borehole 100, and from each such lateral borehole are multiple subsidiary boreholes 201.

FIG. 2 illustrates an example of this process of drilling a number of subsidiary boreholes 201 from one lateral borehole 104. Any number of lateral boreholes 104 can be drilled from one vertical borehole 100 and any number of subsidiary boreholes 201 can be drilled from one lateral borehole 104. However, in implementation it may be that how many boreholes that can and should be used will depend on the angles achieved for optimal coverage and the number of subsidiary boreholes 201 that can be drilled from the lateral borehole increases with distance from the lateral borehole, due to current limitations on directional drilling.

The length between the end of the lateral borehole 104 and the ore body 103 determines the number of subsidiary boreholes 201 that are possible since, as the distance increases, the possible angles to drill optimal subsidiary boreholes 201 increases, resulting in a greater number of subsidiary boreholes 201 that can be used for extraction.

If the end of the vertical borehole 100 is farther away from the orebody 103, a greater number of lateral boreholes 104 and subsidiary boreholes 201 can be drilled. The lateral and subsidiary boreholes are arranged in a pattern such that the volume of extraction is maximized. This pattern requires the boreholes to be closely spaced together, which can be achieved by directionally drilling the lateral and subsidiary boreholes to position and align the boreholes correctly to maximize ore recovery. Excess drilling can be required for a subsequent subsidiary borehole in order to be positioned correctly near the original subsidiary borehole. The section 204 of a subsidiary borehole 201 is defined as the distance between the end of lateral borehole 104 and the beginning of the ore body 103 and is referred to as the waste section of the (subsidiary) borehole. In FIG. 2, the supplementary sections of the boreholes 204 are drilled in order to position the boreholes correctly. As more lateral boreholes 104 are created and back-filled, subsequent lateral boreholes will need to diverge farther away from the orebody and drill through more ground to reach the desired position.

The back-filling step can be used to ensure that the ground surface 105 does not cave-in due to the high number of boreholes being drilled as well as improve recovery in subsequent lateral boreholes. Currently, there are several common methods for backfilling boreholes within the industry that include, but are not limited to: filling the borehole with soil cuttings, filling the borehole with cement grout, filling the borehole with wet or dry bentonite chips, etc.

FIG. 3 depicts the end portion of a lateral borehole 104, which ends a specified distance away from the beginning of the orebody. The ‘current’ subsidiary borehole 201 refers to the borehole which is currently being mined, is depicted with a black colour and extraction-completed subsidiary boreholes which have been back-filled with a back-filling material are shown with a dark grey color. The cased lateral borehole 104 is shown with a light grey colour. A first supplementary borehole 201 can be drilled extending beyond the lateral borehole 104 towards the orebody 103. Ore can be extracted from the orebody and transported to the surface by the lateral borehole. Once the transportation of the ore is complete, the first supplementary borehole is back-filled with a back-filling material (shown in step 2) and a subsequent second subsidiary borehole 202 can be drilled extending beyond the lateral borehole 104 towards the orebody 103. Once the ore is extracted from the orebody and transported to the surface by the second subsidiary borehole 202, the second subsidiary borehole is back-filled with a back-filling material as shown in step 3. In step 3, a third subsidiary borehole 203 can be drilled from which ore 103 can be extracted. The lateral and subsidiary borehole drilling, extracting, transporting, back-filling cycle is repeated until all the ore is extracted. The boreholes can be drilled randomly or in any order, any number of times.

Numerous patterns of closely spaced subsidiary boreholes that can be used in drilling the orebody 103 to maximize the volume of material extracted from the orebody are possible. Patterns of rows of boreholes stacked above one another forming different tiers or stacks, can be created with methods which can include, for example, nested honeycomb patterns (FIG. 4) or direct stacking honeycomb patterns (FIG. 5). The honeycomb type arrangement depicted in FIG. 4 consists of boreholes of the second tier (the one just above the bottom tier) sitting in the grooves created by the bottom tier. Similarly, third-tier boreholes sit in the grooves of the second tier and so on. The direct stacked arrangement depicted in FIG. 5 consists of lines of boreholes stacked directly above the borehole tier below. FIG. 6 shows a side-by-side cross-section comparison of the beehive and direct stacked types of arrangements which can be used to maximize ore recovery. It is noted that only one vertical column of the holes is shown for emphasis and it is to be assumed that the borehole columns can continue in either direction for the length of the orebody.

FIG. 7 illustrates an orthogonal view of correctly positioned end portions 701 of the supplementary boreholes 201 in a nested arrangement aligned within the length of the orebody 103.

A step-by-step cross section of a borehole drilling embodiment is shown in the series of FIGS. 8 to 11. The planned supplementary boreholes 802 are depicted having dashed lines. The grey colored circles indicate extraction-completed boreholes which have been back-filled with a back-filling material. The black colored circles indicate the ‘current’ supplementary borehole which is being mined.

In FIG. 8, the first supplementary borehole 801 is drilled within the orebody 103. As shown in FIG. 9, once the extraction of the ore is complete, the borehole 801 is back-filled with the back-filling material and the next supplementary borehole 901 is drilled directly adjacent to borehole 801. Once borehole 901 is mined and extracted completely, it is back-filled with the back-filling material. Borehole 1001 is then drilled adjacent to 901 (FIG. 10) and the process is repeated (as illustrated in FIG. 11) until the orebody is extracted completely.

The back-filling step can be used to ensure that the ground surface does not cave-in due to the high number of boreholes being drilled as well as improve recovery in subsequent lateral boreholes. Currently, there are several common methods for backfilling boreholes within the industry that include, but are not limited to: filling the borehole with soil cuttings, filling the borehole with cement grout, filling the borehole with wet or dry bentonite chips, etc.

The drill assembly will take the path of least resistance while drilling. If a harder back-filling material is chosen, such as cement, the drill assembly will avoid boring the previously back-filled cement boreholes and continue drilling the rock towards the orebody.

It can be noted that though the embodiment shows the boreholes being drilled in a consecutive manner, this need not be the case. The boreholes can be drilled in any order, including, but not limited to, random, consecutive, outside-in, inside-out, top-down, bottom-up, left-right, right-left etc. The left to right order is shown in FIGS. 12, 13 and 14. The selected arrangement of the borehole system (honeycomb or stacked) pre-determines the projected borehole outlines 802. It can be appreciated that the borehole drilling and backfilling sequence allows one to coordinate the use of the associated equipment such that drilling, and extraction occurs at one location while backfilling occurs at another.

Steps can be taken to create and evaluate a projected surface borehole design. For every orebody, at least one vertical borehole is to be drilled however, it can be possible to drill multiple parent boreholes, spaced apart to maximize recovery of the ore. A process of designing multiple lateral boreholes and evaluating said design is proposed. The process comprising determining drilling parameters, constructing a block model, determining the cut-off grade, designing a borehole layout and evaluating the borehole design.

The drilling parameters can be determined prior to constructing a borehole design. Common drilling parameters can include, but are not limited to: drill rotation speed, bit weight and pressure, hydraulics and fluid flow, etc. Ore properties such as size, grade, mineral composition, hardness, etc. can also affect borehole design. The drill parameters and ore properties can be determined based on prior drilling experience, consultations with specialist drilling companies, or through testing.

Block models, centerlines for each borehole and borehole design layouts can be constructed using advanced mining software. The lateral boreholes can be designed within a specified cut-off in a closely spaced pattern aligned with the long access of the deposit, as depicted in FIG. 5. Finally, the boreholes can be evaluated against the block model, the evaluation can be completed using drilling database software to reconcile volume, tonnage, grade and contained metal.

While designing the borehole layout, it can be of interest to design only the lateral borehole portion of each borehole. The ratio of vertical boreholes to lateral boreholes can vary and depends on the distance between the end of the vertical borehole and the orebody. In one embodiment, a ratio of 1 vertical borehole to 40 lateral boreholes was used, however this number can be increased or decreased based on the properties of the ore. The diameters of the vertical borehole, waste section of borehole or lateral borehole can be determined by completing various geometric design and corresponding economic studies.

For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

The examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.

The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified.

Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims. 

1. A method of directional drilling comprising: drilling a vertical borehole from a surface near an orebody; drilling a lateral borehole extending beyond the vertical borehole towards the orebody; drilling a first subsidiary borehole extending beyond the lateral borehole and into the orebody; extracting ore from the orebody wherein the ore is transported to the surface via the first subsidiary borehole, the lateral borehole and the vertical borehole; back-filling the first subsidiary borehole with a back-filling material; drilling a second subsidiary borehole extending beyond the lateral borehole into the orebody, such that the second subsidiary borehole is positioned adjacent to the first subsidiary borehole; extracting ore from the orebody wherein the ore is transported to the surface via the second subsidiary borehole, lateral borehole and the vertical borehole; and back-filling the second subsidiary borehole with a back-filling material.
 2. The method of claim 1, wherein at least a second lateral borehole is drilled extending beyond the vertical borehole towards the orebody; such that: a subsidiary borehole is drilled extending beyond the second lateral borehole and into the orebody; ore is extracted from the orebody wherein the extracted ore is transported to the surface via the subsidiary borehole, the second lateral borehole and the vertical borehole; and the subsidiary borehole is back-filled with a back-filling material.
 3. The method of claim 2, wherein the method is repeated until the orebody has been substantially fully extracted; drilling subsequent subsidiary boreholes extending beyond the lateral borehole into the orebody; and back-filling the subsequent subsidiary boreholes with a back-filling material after the ore is transported to the surface.
 4. The method of claim 3, wherein the vertical borehole is permanently drilled.
 5. The method of claim 4, wherein the back-filling material is selected from a group consisting of: soil cuttings, cement grout, wet bentonite chips and dry bentonite chips.
 6. The method of claim 3, wherein the first, second and subsequent subsidiary boreholes form a pattern for extracting ore from the orebody.
 7. The method of claim 6, wherein the formed pattern is a nested honeycomb pattern.
 8. The method of claim 6, wherein the formed pattern is a direct stacking honeycomb pattern.
 9. The system of claim 3, wherein the subsequent subsidiary boreholes are spaced apart to maximize recovery of the ore.
 10. A directional drilling system comprising: a vertical borehole; a lateral borehole extending beyond the vertical borehole towards an orebody; and a plurality of subsidiary boreholes extending beyond the lateral borehole and into the orebody; wherein the plurality of subsidiary boreholes form a pattern for extracting ore from the orebody; wherein the ore is transported to the surface via the plurality of subsidiary boreholes, the lateral borehole and the vertical borehole; wherein the plurality of subsidiary boreholes are back-filled with a back-filling material after the ore is transported to the surface.
 11. The system of claim 10, wherein the vertical borehole is permanently installed.
 12. The system of claim 7, wherein the back-filling material is selected from a group consisting of: soil cuttings, cement grout, wet bentonite chips and dry bentonite chips.
 13. The system of claim 10, wherein the formed pattern is a nested honeycomb pattern.
 14. The system of claim 10, wherein the formed pattern is a direct stacking honeycomb pattern.
 15. The system of claim 10, wherein plurality of subsidiary boreholes are spaced apart to maximize recovery of the ore. 